全文获取类型
收费全文 | 4473篇 |
免费 | 11篇 |
国内免费 | 7篇 |
专业分类
航空 | 2093篇 |
航天技术 | 1602篇 |
综合类 | 16篇 |
航天 | 780篇 |
出版年
2021年 | 44篇 |
2019年 | 25篇 |
2018年 | 104篇 |
2017年 | 73篇 |
2016年 | 76篇 |
2015年 | 39篇 |
2014年 | 129篇 |
2013年 | 137篇 |
2012年 | 143篇 |
2011年 | 193篇 |
2010年 | 127篇 |
2009年 | 217篇 |
2008年 | 293篇 |
2007年 | 129篇 |
2006年 | 107篇 |
2005年 | 139篇 |
2004年 | 117篇 |
2003年 | 156篇 |
2002年 | 89篇 |
2001年 | 153篇 |
2000年 | 74篇 |
1999年 | 99篇 |
1998年 | 120篇 |
1997年 | 87篇 |
1996年 | 90篇 |
1995年 | 124篇 |
1994年 | 121篇 |
1993年 | 64篇 |
1992年 | 95篇 |
1991年 | 54篇 |
1990年 | 36篇 |
1989年 | 88篇 |
1988年 | 40篇 |
1987年 | 42篇 |
1986年 | 36篇 |
1985年 | 96篇 |
1984年 | 86篇 |
1983年 | 75篇 |
1982年 | 86篇 |
1981年 | 118篇 |
1980年 | 41篇 |
1979年 | 36篇 |
1978年 | 32篇 |
1977年 | 25篇 |
1976年 | 28篇 |
1975年 | 22篇 |
1974年 | 22篇 |
1973年 | 23篇 |
1972年 | 23篇 |
1971年 | 21篇 |
排序方式: 共有4491条查询结果,搜索用时 62 毫秒
781.
Mohamed Khalil Ben-Larbi Kattia Flores Pozo Tom Haylok Mirue Choi Benjamin Grzesik Andreas Haas Dominik Krupke Harald Konstanski Volker Schaus Sándor P. Fekete Christian Schurig Enrico Stoll 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2021,67(11):3598-3619
782.
Malakhov A. V. Mitrofanov I. G. Litvak M. L. Sanin A. B. Golovin D. V. Djachkova M. V. Nikiforov S. Yu. Anikin A. A. Lisov D. I. Lukyanov N. V. Mokrousov M. I. Shvetsov V. N. Timoshenko G. N. 《Cosmic Research》2022,60(1):23-37
Cosmic Research - The article presents results of ground calibrations of the FREND neutron telescope installed onboard the TGO spacecraft of the Russian-European ExoMars project. The main goal of... 相似文献
783.
J.S. Xu X.J. LiY.W. Liu M. Jing 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2014
Based on measurements of ground-based GPS station network, differences of the mid-latitude ionospheric TEC in the east and west sides of North America, South America and Oceania have been analyzed in this paper. Results show that for nearly all seasons from 2001 to 2010 and in both sides of the longitudes with zero declination, there exist systematic differences for the mid-latitude ionospheric TEC in the regions mentioned above and the features of these differences markedly depend upon the local time but less depend upon seasons and the level of solar activity. Theory analysis shows that the longitude variations of both declination and zonal thermospheric winds are one of important factors to cause differences of the mid-latitude ionospheric TEC in both sides of the longitudes with zero declination. 相似文献
784.
S. V. Novikova 《Russian Aeronautics (Iz VUZ)》2016,59(2):263-270
The paper presents a technique of the neural network model reduction for the GTE operation mode monitoring during bench tests. The technique is based on the conversion of the neural network training task to the of multi-criteria optimization task. 相似文献
785.
I. Artamonova S. Veretenenko 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2014
Changes of troposphere pressure associated with short-time variations of galactic cosmic rays (GCRs) taking place in the Northern hemisphere’s cold months (October–March) were analyzed for the period 1980–2006, NCEP/NCAR reanalysis data being used. Noticeable pressure variations during Forbush decreases of GCRs were revealed at extratropical latitudes of both hemispheres. The maxima of pressure increase were observed on the 3rd–4th days after the event onsets over Northern Europe and the European part of Russia in the Northern hemisphere, as well as on the 4th–5th days over the eastern part of the South Atlantic opposite Queen Maud Land and over the d’Urville Sea in the Southern Ocean. According to the weather chart analysis, the observed pressure growth, as a rule, results from the weakening of cyclones and intensification of anticyclone development in these areas. The presented results suggest that cosmic ray variations may influence the evolution of extratropical baric systems and play an important role in solar-terrestrial relationships. 相似文献
786.
S. Farooq H. Govil 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2014
Crystalline in the Kumaon Himalaya, India near Askot area is a prominent site of the base metal mineralization and gossanised surface. This area is hosted by the sulphides and sulphates of Cu, Pb, Zn and Au and Ag mineralization with the altered rocks like sericite chlorite schist, gneiss etc. Due to the deep weathering this area is also a good illustration site of the gossanised outcrop. 相似文献
787.
O.E. Abe C. Paparini R.H. Ngaya S.M. Radicella B. Nava A. Kashcheyev 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2019,63(10):3177-3188
It is a known fact that ionosphere is the largest and the least predictable among the sources of error limiting the reliability and accuracy of Global Navigation Satellite Systems (GNSS) and its regional augmentation systems like Satellite Based Augmentation System (SBAS) in a safety-of-life application. The situation becomes worse in the Equatorial Ionization Anomaly (EIA) region, where the daytime ionization distribution is modified by the fountain effect that develops a crest of electron density at around ±15° to ±20° of the magnetic equator and a trough at the magnetic equator during the local noon hours. Related to this phenomenon is the appearance of ionosphere irregularities and plasma bubbles after local sunset. These may degrade further the quality of service obtained from the GNSS/SBAS system of the said periods. Considering the present operational augmentation systems, the accuracy and integrity of the ionosphere corrections estimate decreases as the level of disturbances increases. In order to provide a correct ionosphere correction to the user of GNSS operating in African EIA region and meet the integrity requirements, a certified ionosphere correction model that accurately characterizes EIA gradient with the full capacity to over-bound the residual error will be needed. An irregularities detector and a decorrelation adaptor are essential in an algorithm usable for African sub-Saharan SBAS operation. The algorithm should be able to cater to the equatorial plasma vertical drifts, diurnal and seasonal variability of the ionosphere electron density and also should take into account the large spatial and temporal gradients in the region. This study presents the assessment of the ionosphere threat model with single and multi-layer algorithm, using modified planar fit and Kriging approaches. 相似文献
788.
F. Di Capua L. Campajola P. Casolaro M. Campajola A. Aloisio A. Lucaroni G. Furano A. Menicucci S. Di Mascio F. Malatesta M. Ottavi 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2019,63(10):3249-3257
A new methodology for Total Ionizing Dose (TID) tests is proposed. It is based on the employment of an on-chip 90Sr/90Y beta source as alternative to standard methods such as 60Co gamma rays and electrons from LINAC. The use of a compact beta source for TID tests has several advantages. In particular, the irradiation of devices with more than one radiation source results in a better representation of the complex space radiation environment composed of several types, energies and dose-rates. In addition, the use of an easy handling beta source allows the irradiation of electronic devices without any damage to other auxiliary circuit. In this work, 90Sr/90Y beta source dosimetry and related radiation field characteristics are discussed in depth.In order to validate the proposed source for TID tests, a rather complex device such as the “SPC56EL70L5” microcontroller from ST-Microelectronics was exposed to 90Sr/90Y beta rays. The results of this test were compared to that of a previous test of another sample from the same lot with a standard gamma 60Co source. The electronic performances following the two irradiations have been found to be in excellent agreement, by demonstrating therefore the validity of the proposed beta source for TID tests. 相似文献
789.
Cosmic Research - We have considered procedure and results of the experimental study for spectral characteristics of self emission from laboratory models of electric thrusters with closed electron... 相似文献
790.
The techniques of forming the mobile sliding manifolds and vector controls, which bring these systems into the sliding modes under continuous action of uncertain factors, namely limited disturbances and total errors in measurements, are developed for dynamic systems with discontinuous control. The techniques are applicable for effective control of complex aerospace objects. 相似文献